Solar driven ejector heat pumps for supplemental heating and cooling resources

ABSTRACT

In one embodiment, solar-thermal system is provided. The solar-thermal system comprises a generator component; an evaporator component; a heat pump ejector comprising a mixing chamber; said heat pump ejector coupled to the generator component and the evaporator component; wherein the generator component emits a vapor stream into said mixing chamber and the heat pump ejector is configured to extract a working fluid vapor from the evaporator component into said mixing chamber through entrainment thereby to form a mixed flow; and a condenser component configured to cool said mixed flow via a cooling loop.

FIELD

Embodiments of the invention relate to heating and cooling systems.

BACKGROUND

Ejector heat pumps (EHPs) are a decades old technology that was and is applied to refrigeration and air conditioning applications. The common principle behind so-called Rankine refrigeration cycles is that a working fluid (i.e. the refrigerant) can be used to move heat from a lower temperature location to a warmer external environment by compressing the working fluid to raise its temperature above the external environment and subsequently expanding it to drop its temperature to provide the cooling effect. EHPs operate on this principle utilizing a vapor ejector with no moving parts to compress the working fluid instead of a mechanical compressor.

Referring to FIG. 1, a diagram of an exemplary ejector for a heat pump is shown 100. The ejector 100 includes a supersonic nozzle 102. In use, a primary (supersonic) vapor flows 104 into the nozzle 102 where it undergoes expansion. A secondary flow in the form of a low-pressure refrigerant 106 is extracted into the mixing chamber 108 from an evaporator (not shown) via entrainment causing the supersonic flow 104 to decelerate. As the supersonic flow 104 decelerates, it compresses the entrained refrigerant vapor 106 to form a mixed flow 110 within mixing chamber 108 that is output to a condenser configured to reject heat to the external environment.

Ejector heat pumps are appealing for several reasons, including the fact that the device functions as a compressor without any moving parts leading to increased reliability, longer lifetimes, and potentially lower costs than compressors with moving parts. One of the challenges of ejector heat pumps is that its coefficient of performance (COP) is lower than that of a mechanical compressor-based heat pump. The COP is defined as the ratio of energy input to energy transferred. A COP of 1.5 uses 1 unit of energy to move 1.5 units of heat. EHPs are generally capable of achieving COPs as high as 1.5 while mechanical heat pumps can achieve COPs of 2 or more.

SUMMARY

This Summary is provided to comply with 37 C.F.R. § 1.73, requiring a summary of the invention briefly indicating the nature and substance of the invention. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

According to a first aspect of the invention, there is provided a solar-thermal system, comprising:

-   -   a generator component;     -   an evaporator component;     -   a heat pump ejector comprising a mixing chamber; said heat pump         ejector coupled to the generator component and the evaporator         component; wherein the generator component emits a vapor stream         into said mixing chamber and the heat pump ejector is configured         to extract a working fluid vapor from the evaporator component         into said mixing chamber through entrainment thereby to form a         mixed flow; and     -   a condenser component configured to cool said mixed flow via a         cooling loop.

According to a second aspect of the invention, there is provided a method for operating a solar-thermal system, comprising:

-   -   generating a vapor stream in a generator component using heat         extracted from a solar thermal collector array;     -   feeding said vapor stream into an ejector heat pump comprising a         mixing chamber;     -   forming a mixed flow in said mixing chamber by extracting a         secondary flow into said mixing chamber through entrainment,         wherein said secondary flow comprises a working fluid vapor from         an evaporator component; and     -   condensing said mixed flow in a condenser loop wherein heat is         extracted from said mixed flow.

Other aspects and example embodiments are provided in the drawings and the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form only in order to avoid obscuring the invention.

The present invention, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict exemplary embodiments of the invention. These drawings are provided to facilitate the reader's understanding of the invention and shall not be considered limiting of the breadth, scope, or applicability of the invention. It should be noted that for clarity and ease of illustration these drawings are not necessarily made to scale

FIG. 1 is a schematic drawing of the heat pump.

FIG. 2 is a schematic drawing of a solar-thermal system for heating water, in accordance with one embodiment of the invention.

FIG. 3 is a schematic drawing of a solar-thermal system for cooling and a conditioning unit, in accordance with one embodiment of the invention.

The figures are not intended to be exhaustive or to limit the invention to the precise form disclosed. It should be understood that the invention can be practiced with modification and alteration, and that the invention be limited only by the claims and the equivalents thereof.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form only in order to avoid obscuring the invention.

Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearance of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not other embodiments.

Moreover, although the following description contains many specifics for the purposes of illustration, anyone skilled in the art will appreciate that many variations and/or alterations to said details are within the scope of the present invention. Similarly, although many of the features of the present invention are described in terms of each other, or in conjunction with each other, one skilled in the art will appreciate that many of these features can be provided independently of other features. Accordingly, this description of the invention is set forth without any loss of generality to, and without imposing limitations upon, the invention.

The teachings and principles of the present invention are applicable to a wide variety of heating and cooling resources. For purposes of explanation and illustration, however, the present invention is hereafter described in reference to particular embodiments of heating and cooling systems. However, it should be understood, that one of ordinary skill in the art will, upon reference to this description, would be able to apply the principles and teachings of the present invention in a wide variety of such heating and cooling systems.

Referring now to FIG. 2 of the drawings, a solar water heating (SWH) system 200, in accordance with one embodiment of the invention is shown. The system 200 is configured to convert sunlight into heat which can then be used to heat water for residential or commercial uses, as will be explained. The system 200 includes a solar thermal collector array 201 configured to supply heat in the form of a heated fluid or gas stream 202 to a heat exchanger 204. Any remaining heat in the fluid or gas stream may be further extracted as it passes through a heat exchanger 238. This heat can be used to boil a working fluid in a generator 206. The generator 206 may also contain a reservoir of hot fluid (not shown) so that its operation may be continuous even if there are variations in sunlight that results in variations in output from collector array 201. The generator 206 emits a vapor stream 208 to an ejector 210. In one embodiment, the ejector 210 is of a design that is similar to the design of the ejector described with reference to FIG. 1. In use, the ejector 210 entrains a working fluid vapor 212 from an evaporator 214. This entrainment process cools the evaporator 214 which enables it to extract heat from the atmosphere via a heat exchanger 218 which is exposed to outdoor air 220. Heat from both the collector array 201 and the outdoor air 220 is combined in a compressed vapor flow 222 which is then condensed in a condenser 224. Thus, the condenser 224 becomes heated. A thermal storage fluid contained within a thermal storage tank 236, is pumped from the bottom of the tank 236 via a pump 232 through heat exchanger 230 which allows the fluid to extract heat from the condenser 224, thereby raising the fluid's temperature. The fluid continues on to a heat exchanger 238 where it gains additional heat from that remaining in the fluid or gas stream from the collector array 201, thereby raising its temperature further. The heated fluid is then returned to the tank 236 via a tank input 234.

Over the course of the day the fluid in the thermal storage tank 236 is heated and the stored heat can then be used for some purpose within a residence, a commercial business, or some other useful application that requires heat. Overall the use of the ejector heat pump 210 in the system 200, which comprises the components contained within shaded box 240, enables an increase in the amount of heat which may be collected from the environment by some factor determined by the COP. Thus, for example, if a system without the ejector heat pump is capable of collecting 1 kW of power from the sun, and the COP of the system was 1.3, then the amount of power collected from both the sun and the atmosphere would be 1.3 kW. Advantageously, heat pumps used for conventional air conditioning and cooling have exhibited lifetimes in the field of up to forty years. This makes them very attractive components to be added to a SWH system which has an expected lifetime of 25 years.

Referring again to FIG. 2, in one embodiment, all of the components to the left of the heat exchanger 238 would reside on a rooftop whereas the thermal storage tank on the right would reside on the interior or ground level of the structure for which the hot water is intended.

Referring now to FIG. 3 of the drawings, another embodiment of a system 300 incorporating a solar thermal driven ejector heat pump is illustrated. The system 300 includes a solar thermal collector array 301 configured to supply heat in the form of a heated fluid or gas stream 302 to heat and exchanger 304. This heat is used to create a vapor stream within a generator 306 and the resulting stream 308 is used to drive an ejector 310, which is similar in design to the ejector 210. The generator 306 may also contain a reservoir of hot fluid (not shown) so that its operation may be continuous even if there are variations in sunlight which cause variable output from collector array 301. The ejector 310 entrains vapor from an evaporator 314, cooling it in the process. This enables the evaporator 314 to extract heat from a condenser loop 320, 322, via a heat exchanger 318. In one embodiment, the condenser loop 320, 322 may be a component of a packaged air conditioning system 324. In one embodiment, this air conditioning system may be a roof-mounted unit that may be used for buildings which have large available roof space for such components though it may be a ground or even window mounted unit. Heat from the collector array 301 is used to produce a compressed vapor stream 326 which is condensed in a condenser heat exchanger 328. The condenser heat exchanger 328 may be exposed to air 338 which is the medium to which the total heat output is rejected.

Normally rooftop units reject heat from the inside of a building via an air-to-liquid heat exchanger 340 which allows heated fluid (the refrigerant) within the condenser loop to be cooled by interaction with outside air. Coupling the heat exchanger 318 to the condenser loop provides an additional means for extracting heat as the refrigerant experiences additional cooling by being coupled to the evaporator 314 via the heat exchanger 318 and the condenser loop 320, 322. Advantageously, this heat extraction or cooling resource takes some of the burden of the packaged air conditioning unit 324, and thus reduces the electricity required for it to perform the equivalent cooling resource to the building it serves. The overall result is that by using this configuration solar energy may be effectively coupled or retrofitted to an existing air conditioning system in a way which helps to reduce the overall electrical load of the air-conditioning system, thus saving energy and cost. The evaporator 314 may also include or be coupled to a cool thermal storage reservoir. In this way, the cooling resource produced by the ejector heat pump may be accumulated over the course of the day and then applied to reducing the load on the air conditioning system at a time which may be more appropriate, for example when electricity costs are highest. This cool thermal storage reservoir may take the form of an insulated tank of water and or a phase change medium.

Other thermally driven refrigeration cycles may be used in the supplemental cooling and heating applications described above. These include but are not limited to single and multi-effect absorption cycles, adsorption cycles, solid and liquid based desiccant cycles, thermochemical cycles as well as duplex rankine cycles. While these solutions differ in their complexity, cost, and performance, they have the ability to be driven by a heat source of some kind. As such they can find use in these applications if their innate characteristics might somehow make them a more appropriate choice under different circumstances.

Numerous specific details may be set forth herein to provide a thorough understanding of a number of possible embodiments of a digital imaging system incorporating the present disclosure. It will be understood by those skilled in the art, however, that the embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the embodiments. It can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments.

Although the invention is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the invention, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments.

Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.

The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term “module” does not imply that the components or functionality described or claimed as part of the module are all configured in a common package. Indeed, any or all of the various components of a module, whether control logic or other components, can be combined in a single package or separately maintained and can further be distributed in multiple groupings or packages or across multiple locations. 

1. A solar-thermal system, comprising: a generator component; an evaporator component; a heat pump ejector comprising a mixing chamber; said heat pump ejector coupled to the generator component and the evaporator component; wherein the generator component emits a vapor stream into said mixing chamber and the heat pump ejector is configured to extract a working fluid vapor from the evaporator component into said mixing chamber through entrainment thereby to form a mixed flow; and a condenser component configured to cool said mixed flow via a cooling loop.
 2. The solar-thermal system of claim 1, wherein said cooling loop is configured to heat water stored in a thermal storage unit.
 3. The system of claim 1, further comprising a solar thermal collector array configured to supply heat to the generator component thereby to facilitate generation of the vapor stream by the generator component.
 4. The system of claim 1, wherein the evaporator component extracts heat from outdoor air.
 5. The system of claim 1, wherein the evaporator component extracts heat from an air-conditioning unit.
 6. The system of claim 1 wherein said generator component, evaporator component, and heat pump ejector are installed on the rooftop of a building.
 7. The system of claim 3, wherein said thermal storage unit is installed and ground level.
 8. The system of claim 1, wherein said cooling loop comprises a first heat exchanger coupled to said condenser component; and a second heat exchanger configured to extract heat from the solar thermal collector array.
 9. A method for operating a solar-thermal system, comprising: generating a vapor stream in a generator component using heat extracted from a solar thermal collector array; feeding said vapor stream into an ejector heat pump comprising a mixing chamber; forming a mixed flow in said mixing chamber by extracting a secondary flow into said mixing chamber through entrainment, wherein said secondary flow comprises a working fluid vapor from an evaporator component; and condensing said mixed flow in a condenser loop wherein heat is extracted from said mixed flow.
 10. The method of claim 9, wherein said condenser loop comprises a first heat exchanger coupled to a condenser component; and a second heat exchanger configured to extract heat from the solar thermal collector array.
 11. The method of claim 10, further comprising pumping water from a thermal storage unit to said first and second heat exchangers thereby to cause said wanted to be heated using the heat extracted from the mixed flow.
 12. The method of claim 9, wherein the evaporator component is configured to extract heat from outdoor air.
 13. The method of claim 9, wherein the evaporator component is configured to extract heat from an air-conditioning system.
 14. The method of claim 10, further comprising locating the thermal storage unit and ground level.
 15. The method of claim 10, further comprising locating the generator component, the ejector heat pump, and the evaporator component on the rooftop of a building. 